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What blood tests will I be offered?

Blood tests are a routine part of your antenatal care in pregnancy. When you go for your booking appointment, either with your midwife or your GP, you’re likely to be offered some or all of the following blood tests. This is to check, among other things, your blood group, whether you have any infections or diseases and whether your baby has any fetal abnormalities.

All blood tests you are offered are optional. Your GP or midwife will explain to you what they are, so you can decide whether or not you want to have them.

It’s natural to be worried about them but blood tests give you and your midwife or doctor important information about your health. They can also highlight any potential problems in your pregnancy.

Blood group

Your blood group is important to know, just in case you need a transfusion during pregnancy or birth. Blood group O is the most common. Groups A, B, and AB are less so.

If you're rhesus negative and your baby's dad is positive, there's a good chance your baby will be rhesus positive, too. In this case, your body may produce antibodies that start to attack your baby's red blood cells. Injections of a substance called immunoglobulin, given at 28 weeks, should prevent this happening (NCCWCH 2008). Read more about what it means to be rhesus negative.

Haemoglobin levels

A blood test can tell you if your haemoglobin levels are low, which is a sign of iron-deficiency anaemia. Your body needs iron to produce haemoglobin to carry oxygen around the body in your red blood cells.

If you're anaemic due to iron deficiency, your GP or midwife will talk to you about the best foods to eat to boost your iron stores. She's also likely to prescribe iron tablets, as this is the best way to treat anaemia in pregnancy (Pavord et al 2012).

Your haemoglobin levels will be checked again at 28 weeks (NCCWCH 2008). If you suffer a lot from tiredness or are carrying twins or more (NCCWCH 2011), your midwife will arrange for a blood test earlier to see if you're anaemic.

Immunity to German measles (rubella)

Most mums-to-be are immune to German measles. Either they've been vaccinated against it, or they've had the disease as a child.

If you aren't immune, you'll be advised to have a vaccination against the disease once your baby’s born. It's important to avoid anyone who has or may have the infection while you're still pregnant (NCCWCH 2008). If you catch German measles during pregnancy, your baby's heart, sight and hearing may be seriously affected.

Hepatitis B

A blood test is often the only way to find out for certain if you’re a carrier of the hepatitis B virus. If you pass the disease on to your baby before or after he’s born, he will need to be protected with a series of injections of vaccine and antibodies, starting as soon as he’s born (DH 2011, NCCWCH 2008, NHS UK NSC 2014). A blood test at one year of age is used to check whether he has avoided the infection.

Syphilis

Thankfully, this sexually transmitted disease is rare nowadays. However, if you have it and it isn't treated during pregnancy, it could cause abnormalities in your baby. Syphilis can also cause a baby to be stillborn (NHS UK NSC 2014).

The blood test for syphilis can sometimes produce a false positive result. This is because it's hard to tell the bacteria that cause syphilis from other similar bacteria that commonly cause non-sexually transmitted diseases (NCCWCH 2008).

If you're diagnosed with syphilis, you'll be treated with penicillin (NCCWCH 2008). This may be enough to protect your baby from the disease, although some babies need antibiotics after the birth (NHS UK NSC 2014).

HIV/AIDS

All mums-to-be are offered a blood test to detect HIV and AIDS. You can turn it down if you want to. However, knowing that you have the infection means that steps can be taken to reduce the chance of the virus being transmitted to your baby (NCCWCH 2008, NHS UK NSC 2014). Find out more about HIV and AIDS in pregnancy.

Will I be tested for blood-cell disorders?

You should be offered a test for sickle-cell disease or thalassaemia at your booking appointment if there is a chance that you have these disorders. They can make you anaemic and can be passed on to your baby.

In the UK, sickle-cell disorders are more common in people of African and African-Caribbean descent. Thalassaemia is more common in people of Asian, Mediterranean, Middle Eastern or African descent.

In most parts of the UK, all pregnant women are offered a test for thalassaemia (NCCWCH 2008, NHS UK NSC 2012, 2014). However, there are different approaches to screening for sickle-cell disease, depending on how commonly the condition occurs in a particular area (NCCWCH 2008, NHS UK NSC 2014). All pregnant women are offered screening in areas where a lot of people have the condition.

If you live in an area where not many people have thalassaemia, your midwife or doctor may ask you to fill out a questionnaire about your family origins. This will help them to decide whether to offer you the test for sickle-cell disease (NCCWCH 2008, NHS UK NSC 2014).

What other blood-screening tests will I be offered?

All pregnant women should be offered a screening test for genetic abnormalities, such as Down's syndrome, in their baby (NCCWCH 2008). One of the most accurate tests is the combined screening test. This consists of blood tests and nuchal translucency scan carried out at the end of the first trimester.

This combined test is now recommended throughout the UK (NCCWCH 2008, NHS FASP. 2011). It gives you a more reliable risk rating that your baby may have a problem than the traditional triple or quadruple blood tests (NCCWCH 2008, NHS FASP. 2011).

In some NHS trusts in the UK, including Northern Ireland (Lynn et al 2010, NHS UK NSC 2012) and Wales (BBC News Wales 2014), the combined test may not yet be available.

Screening tests cannot tell you for certain that your baby has a problem. If you want to be certain, you need to go on to have a diagnostic test, such as CVS or amniocentesis. Find out more about screening for Down's syndrome.

Can I request additional tests?

Tests for the following conditions aren't routinely offered, but you can request blood tests for them if you think you're at particular risk.

Toxoplasmosis is an infection spread through cat poo, soil and undercooked meat. If the infection is caught for the first time during pregnancy, it can damage a developing baby. This may lead to miscarriage or cause a baby to be stillborn. Find out how you can avoid toxoplasmosis infection (NCCWCH 2008, NHS Choices 2013).

Group B strep can make some newborn babies very ill if they catch it during birth (NCCWCH 2008, RCOG 2012). If you’re worried about this, ask to be tested or arrange a private test late in pregnancy at about 35 weeks to 37 weeks. This way, if you test positive, steps can be taken to prevent your baby from being affected.

If you have good reason to think you may have contracted hepatitis C, you can request a blood test for it. You may be at risk if you:

had a blood transfusion before blood screening was introduced in 1992

have a history of injecting drugs

have tattoos or body piercings

(NCCWCH 2008)

If you do have hepatitis C, you'll be referred for counselling and treatment with a specialist (NCCWCH 2008).

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Comments

Hi i gave bloods at my 20weeks scan and i dont know why im scared i might have HIV because I had a cold for a week and now ive got pains in my joints you read these symptoms online Im 22 weeks pregnant can someone please ease my mind If i had HIV would my midwife contact me quickly

hi i was wondering if anyone can help? i'm 28 weeks pregnant but at 27 weeks i had routine bloods taken and then got a phone call today to be asked to go for repeat tests, she said it's nothing to worry about but i can't stop thinking about it and whether there is something to worry about. please help put my mind at rest.

Just wonderin if anyone can help me I had a blood test from my midwife and a wee test and they both come back borderline no further action what does this mean anythin bad please help wasn't for pregnancy was for antibodies and infections and stuff

I'm a hypertensive sufferer. My blood pressure is normally anything from 170/109 , 150/99,149/105, but since being on hypertone its being varying from 123/76 to 136/90. How will this affect my pregnancy?

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